1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory and a method of manufacturing the same and, more particularly, to a flash memory.
2. Description of the Related Art
Nonvolatile semiconductor memories such as NAND type flash memories are mounted on various electronic equipments. Further, such a nonvolatile semiconductor memory is constituted of a circuit including transistors and resistance elements. The resistance element is required to have a high resistivity for the purpose of chip size reduction, and enable a stable characteristic to be obtained, and various manufacturing methods are studied (for example, Jpn. Pat. Appln. KOKAI Publication No. 9-92736).
As one of the manufacturing methods, there is a technique in which a resistor of a resistance element is formed of the same material as that of the floating gate electrode of a memory cell transistor simultaneously with the floating gate electrode thereof.
However, in the floating gate electrode, a polysilicon film having a high impurity concentration and a low resistivity is used so as to avoid depletion of the gate. For this reason, it is impossible to avoid using a resistor having a high impurity concentration, thereby lowering the resistivity of the resistor.
Accordingly, in order to obtain a desired resistance value, in the shape of the resistor, a length must be long, and the line width (cross section) must be small.
Therefore, an area on a chip occupied by the resistance element is increased and the line width is made small, thereby making it also difficult to obtain a stable resistance value.